Insulation for -25C 3

[MedicineEng]

Dear All:
I have brine pipelines in my site that are usually at -25C. Since my site is located in a subtropical region (very humid and hot weather), what happens is that most of the year I have lots of condensation in those pipes, that provoke energy ineficiency and cause disturbance in production areas. Actually these lines are insulated with green phenolic foam with vapour barrier and SS cladding. The fact is that I am already here for almost 3 years and there were insulations that were already replaced 2 times but the problem remains. My subcontractor says that the material specification is Ok, but I am having my doubts. Which type of materials would you recomend?
Just one remark: since my site works with some flamable products, I need insulation that in case of fire doesn't provoke toxic smoke.

Thanks a lot for your help.

PR

 

[MikeHalloran]

I'm wondering if it would be effective to slightly pressurize the vapor barrier with conditioned air, so less moisture would be available to condense at the pipe surface.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[MedicineEng]

Mike:
Thanks a lot for your input, but I don't think that this is possible since I have brine pipeline spread all over the site, counting hundrends and hundreds of meters.

PR

 

[MikeHalloran]

Sorry, I must have misunderstood the problem.

Care to reveal the specific dimensions of a typical cross section?





Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[MedicineEng]

Mike:
My main brine pipe is 4" but then I have reduction to the equipments that can go down to 1 1/2".

Thanks.
PR

 

[Montemayor]

Paulo:

I've installed and operated Liquid CO2 (-29 oC), liquid NH3 (-33 oC), as well as liquid Oxygen, liquid Nitrogen & various refrigerant lines and equipment in the Caribbean (from Jamaica to Trinidad), in South America (Colombia, Venezuela, Peru, Bolivia, & Chile) and never experienced any problems with the insulation I specified and installed. I've used Styrofoam, foamed Urethane and FoamGlas types of insulation. For your application, I'd recommend the FoamGlas.

But whichever insulation type you employ, it is essential and very important to install a sucessful and reliable vapor barrier. Cold insulation, regardless of the type will fail miserably in not installed with a secure and reliable vapor barrier. That's the whole secret. I never used metal sheathing - even in the Amazon Basin. And my piping never formed external condensation. You have to calculate and apply the correct insulation thickness as well. FoamGlas, being composed of glass, will not burn.

I consider having to install insulation 2 times in 3 years in the middle of the Amazon jungle as an engineering failure. Something is being done wrong. It is either the insulation specifications or the installation - or both.

I hope this experience helps you out.

 

[25362]

[♣] Don't leat people walk on the insulated pipes,
probably penalizing the vapor barrier.
[♣] Insulate flanges, and protruding surfaces.
[♣] Keep away humidity: don't install the insulation
over wet pipes or under rain.
[♣] Avoid thermal shocks ([≥]70^oC/h)
[♣] Follow Art Montemayor's advice.

Phenolic foams have a comparatively higher water absorption and may enable vapor ingress by means of the processes of absorption, condensation, hygroscopicity, permeability and capillary action, probably caused by their higher friability which, BTW, may cause debonding in sandwich structures.

 

[pmover]

just had to give a star to Art and 25362 . . .

vapor barrier is crucial as is sealing ends and longitudal seams. foamglas insulation is a suitable insulation for cold piping - used in cyrogenic gas plants along gulf coast and other high humidity areas.

good luck!
-pmover

 

[quark]

Do you observe condensation on metal cladding? If your piping insulation is not designed keeping metal cladding in mind, you may have problems with condensation due to low emittance of cladding. This tries to keep the cladding surface temperature low and subsequent chances of condensation.

The insulation manufacturer can throw some calculated figures about this issue.

For example, closed cell neoprene insulation designed for still air and with inside(duct) air temperature of 8⁰C gives 8mm thickness but when the insulation is cladded with 40gauge aluminium, the thickness goes as high as 12mm to prevent condensation. I have been speaking to Armaflex for a detailed calculation but what I got was a case study, so far.

Regards,

 

[quark]

I forgot to add, this link gives you some idea

http://www.extolohio.com/DATA/ARTICLES/emittance.html

 

[MedicineEng]

Thank you all guys.
Now, just one thing:
How can I check the minimum thickness of phenolic foam do I need to insulate a 4"pipe at -25C with metal sheet cladding?

Thanks.
PR

 

[Montemayor]

Paulo:

You and I know you that the answer to last query is: you do your conventional calculations for heat transfer. One good source for a timely tutorial is:

http://www.cheresources.com/insulationzz.shtml

I hope I've been of some help. I respect your qualifications and your intelligent queries in prior postings, and I feel you're more than qualified to resolve this conventional heat transfer problem.
Muita sorte

 

[MedicineEng]

Montemayor:
Here's a star and
Muito Obrigado.

 

[unclesyd]

One additional step we used on all our piping subject to condensation was to use a Cold Tar Epoxy on CS and a Silicate based material on SS.



Montemayor,
You had me going for a minute thinking you were going to recommend Cork.

 

[Montemayor]

Uncle Sydney:

The only cork I employ nowadays is on my wine bottles.

But you're on the right track; I used cork in NH3 refrigeration systems. All of it was gone by the time I'd been in the plants for 15 years and I was responsible for stripping a lot of it out. Some of the young whippersnappers on the Forum are probably shaking their heads right now, wondering what in the world we're writing about.....

 

[quark]

The emissivity value of SS given in the link provided by Mr Montemayor may be a bit high for a finished SS surface. For a mill finish this can be ok but for polished surfaces it is as low as 0.2. My suggestion is to consider the highest dew point temperature. This can be an overkill if we just consider average dew point data based on ASHRAE design conditions. One more FOS is to consider still air. Thus, you can minimize the effects of condensation.

Unclesyd and Montemayor,

I thought you both were talking of sharing a vine
Cork insulation is new to me though it is an old technique.

Regards,

 

[25362]

Some 30 years ago I visited a -now "extinct"- relatively small lube oil refinery in the Balkan peninsula actually using Mediterranean cork for cold insulation of its rotary vacuum filters in a solvent oil-dewaxing plant.

 

[sterl]

I would suggest that there are treatments applied to Foamglas and its variants that retard mould and decrease the fretting and ratcheting phenomena that attack VB films. Also from an insulation decay standpoint: the support points, chair construction, contraction constraints and saddles need to be considered...and if your pipes are on shoes, you might consider a different retention method.

As to Cork Insulation: don't act so octegenarian, boys. Lots of Cold Storage Warehouses and Ice Houses right up through 1960 were insulated with Slab Cork. And there are many ice silos standing alongside rail sidings today in California and Oregon that use Red Wood Bark and in a couple of cases, dried seaweed as insulation. One building I know of was re-insulated with dried silage, that is chopped up corn stalks...

The larger difficulty: Both the binder used in making slab cork, and the installation techniques that usually involved Tar or Asphalt, were highly flammable...and the cork only net contributed to the effect. Not very long ago, we built a large High Visibility beverage vendor's showroom and the exposed surfaces were blond cork.

Insurance Companies and Corning killed cork as a commercial insulation material. I wouldn't think of it as the ideal material for pipe insaulation in the Amazon Jungle...

 

[unclesyd]

This may be the answer, RG 2400. Forget their website approach and checkout their literature.
They make some good products such as the Peel and Stick. I definitely would give them a call.

http://www.rg2400.com/weapons/literature.html

Here is the home page of the RG 2400 manufacturer “PolyGuard”.

http://www.polyguardproducts.com/

Montemayer,

Circumstances have forced me to the lower shelves where plastic prevails.

sterl,
Agree completely with the use of Cork in this application.
Still a few ice plants along the coast that produce 300# blocks of ice the old fashion way with NH3 refrigeration and circulating brine as the freezing medium with every thing being cork insulated. Several of these plants used to sit dockside.